SEDIMENTARY CHARACTERISTICS OF DRIFTING SEDIMENTS ABOVE AN ERODING LOESSAL SANDY LOAM SOIL AS AFFECTED BY MECHANICAL DISTURBANCE

Our understanding of the physical mechanisms of wind erosion and dust emission stimulated by disturbance of surface soils is not adequate, e ven though it is a problem leading to desertification in the arid zone . Simulations of the influence of surface soil disturbance ratios on w ind erosion and sedimentary characteristics of an eroded loessal sandy loam soil were conducted in an indoor wind tunnel. The results showed that the grain-size composition of the drifting soil was finer than, though similar to, the original soil, as the surface disturbance ratio increased. Wind erosion on the loessal sandy loam soil was selective. The eroded sediments were poorly sorted and became poorer with increa ses in the disturbance ratio and wind speed. The relative proportion o f suspension population increased with increasing disturbance ratio. S everal parameters such as the pattern of the frequency distribution cu rves, skewness and kurtosis reflected the dependence of the sedimentar y characteristics of the drifting sediments on the eroding source soil . Soil erosion and dust emission by wind in drylands can be reduced by reducing unnecessary mechanical disturbance during erosion seasons. ( C)1998 Academic Press Limited.